4 Answers
4

As others have mentioned, rename is good at this, but read the man page (man rename) before you try it. There are at least two entirely different tools out there called rename and which one you have will depend on your distribution. Calling them incorrectly can be dangerous.

Here's the man page for the perl-based version by Larry Wall that ships with Ubuntu. You give it a perl expression like rename 's/\.sql$/.php/' *.sql

Here's the man page for the rename that ships with older Red Hat and CentOS distributions. Usage is simple string substitution like rename .sql .php *.sql

You could also use a bash one-liner to process each file one at a time: